| Message ID | 20240910190822.2407606-1-johunt@akamai.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v3] tcp: check skb is non-NULL in tcp_rto_delta_us() | expand |
On Tue, Sep 10, 2024 at 3:08 PM Josh Hunt <johunt@akamai.com> wrote: > > We have some machines running stock Ubuntu 20.04.6 which is their 5.4.0-174-generic > kernel that are running ceph and recently hit a null ptr dereference in > tcp_rearm_rto(). Initially hitting it from the TLP path, but then later we also > saw it getting hit from the RACK case as well. Here are examples of the oops > messages we saw in each of those cases: ... > The NULL ptr deref is coming from tcp_rto_delta_us() attempting to pull an skb > off the head of the retransmit queue and then dereferencing that skb to get the > skb_mstamp_ns value via tcp_skb_timestamp_us(skb). > > The crash is the same one that was reported a # of years ago here: > https://lore.kernel.org/netdev/86c0f836-9a7c-438b-d81a-839be45f1f58@gmail.com/T/#t > > and the kernel we're running has the fix which was added to resolve this issue. > > Unfortunately we've been unsuccessful so far in reproducing this problem in the > lab and do not have the luxury of pushing out a new kernel to try and test if > newer kernels resolve this issue at the moment. I realize this is a report > against both an Ubuntu kernel and also an older 5.4 kernel. I have reported this > issue to Ubuntu here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2077657 > however I feel like since this issue has possibly cropped up again it makes > sense to build in some protection in this path (even on the latest kernel > versions) since the code in question just blindly assumes there's a valid skb > without testing if it's NULL b/f it looks at the timestamp. > > Given we have seen crashes in this path before and now this case it seems like > we should protect ourselves for when packets_out accounting is incorrect. > While we should fix that root cause we should also just make sure the skb > is not NULL before dereferencing it. Also add a warn once here to capture > some information if/when the problem case is hit again. > > Fixes: e1a10ef7fa87 ("tcp: introduce tcp_rto_delta_us() helper for xmit timer fix") > Signed-off-by: Josh Hunt <johunt@akamai.com> > --- > > v3: Added fixes tag and more packet accounting info as requested by Neal Cardwell. > Also updated rto calcs to reflect original code. > v2: Removed cover letter and added context from original cover letter to > commit msg. > > include/net/tcp.h | 21 +++++++++++++++++++-- > 1 file changed, 19 insertions(+), 2 deletions(-) > > diff --git a/include/net/tcp.h b/include/net/tcp.h > index 2aac11e7e1cc..196c148fce8a 100644 > --- a/include/net/tcp.h > +++ b/include/net/tcp.h > @@ -2434,9 +2434,26 @@ static inline s64 tcp_rto_delta_us(const struct sock *sk) > { > const struct sk_buff *skb = tcp_rtx_queue_head(sk); > u32 rto = inet_csk(sk)->icsk_rto; > - u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto); > > - return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp; > + if (likely(skb)) { > + u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto); > + > + return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp; > + } else { > + WARN_ONCE(1, > + "rtx queue emtpy: " > + "out:%u sacked:%u lost:%u retrans:%u " > + "tlp_high_seq:%u sk_state:%u ca_state:%u " > + "advmss:%u mss_cache:%u pmtu:%u\n", > + tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out, > + tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out, > + tcp_sk(sk)->tlp_high_seq, sk->sk_state, > + inet_csk(sk)->icsk_ca_state, > + tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache, > + inet_csk(sk)->icsk_pmtu_cookie); > + return jiffies_to_usecs(rto); > + } > + > } Looks good to me. Thanks, Josh! Acked-by: Neal Cardwell <ncardwell@google.com> neal
diff --git a/include/net/tcp.h b/include/net/tcp.h index 2aac11e7e1cc..196c148fce8a 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -2434,9 +2434,26 @@ static inline s64 tcp_rto_delta_us(const struct sock *sk) { const struct sk_buff *skb = tcp_rtx_queue_head(sk); u32 rto = inet_csk(sk)->icsk_rto; - u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto); - return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp; + if (likely(skb)) { + u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto); + + return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp; + } else { + WARN_ONCE(1, + "rtx queue emtpy: " + "out:%u sacked:%u lost:%u retrans:%u " + "tlp_high_seq:%u sk_state:%u ca_state:%u " + "advmss:%u mss_cache:%u pmtu:%u\n", + tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out, + tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out, + tcp_sk(sk)->tlp_high_seq, sk->sk_state, + inet_csk(sk)->icsk_ca_state, + tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache, + inet_csk(sk)->icsk_pmtu_cookie); + return jiffies_to_usecs(rto); + } + } /*
We have some machines running stock Ubuntu 20.04.6 which is their 5.4.0-174-generic kernel that are running ceph and recently hit a null ptr dereference in tcp_rearm_rto(). Initially hitting it from the TLP path, but then later we also saw it getting hit from the RACK case as well. Here are examples of the oops messages we saw in each of those cases: Jul 26 15:05:02 rx [11061395.780353] BUG: kernel NULL pointer dereference, address: 0000000000000020 Jul 26 15:05:02 rx [11061395.787572] #PF: supervisor read access in kernel mode Jul 26 15:05:02 rx [11061395.792971] #PF: error_code(0x0000) - not-present page Jul 26 15:05:02 rx [11061395.798362] PGD 0 P4D 0 Jul 26 15:05:02 rx [11061395.801164] Oops: 0000 [#1] SMP NOPTI Jul 26 15:05:02 rx [11061395.805091] CPU: 0 PID: 9180 Comm: msgr-worker-1 Tainted: G W 5.4.0-174-generic #193-Ubuntu Jul 26 15:05:02 rx [11061395.814996] Hardware name: Supermicro SMC 2x26 os-gen8 64C NVME-Y 256G/H12SSW-NTR, BIOS 2.5.V1.2U.NVMe.UEFI 05/09/2023 Jul 26 15:05:02 rx [11061395.825952] RIP: 0010:tcp_rearm_rto+0xe4/0x160 Jul 26 15:05:02 rx [11061395.830656] Code: 87 ca 04 00 00 00 5b 41 5c 41 5d 5d c3 c3 49 8b bc 24 40 06 00 00 eb 8d 48 bb cf f7 53 e3 a5 9b c4 20 4c 89 ef e8 0c fe 0e 00 <48> 8b 78 20 48 c1 ef 03 48 89 f8 41 8b bc 24 80 04 00 00 48 f7 e3 Jul 26 15:05:02 rx [11061395.849665] RSP: 0018:ffffb75d40003e08 EFLAGS: 00010246 Jul 26 15:05:02 rx [11061395.855149] RAX: 0000000000000000 RBX: 20c49ba5e353f7cf RCX: 0000000000000000 Jul 26 15:05:02 rx [11061395.862542] RDX: 0000000062177c30 RSI: 000000000000231c RDI: ffff9874ad283a60 Jul 26 15:05:02 rx [11061395.869933] RBP: ffffb75d40003e20 R08: 0000000000000000 R09: ffff987605e20aa8 Jul 26 15:05:02 rx [11061395.877318] R10: ffffb75d40003f00 R11: ffffb75d4460f740 R12: ffff9874ad283900 Jul 26 15:05:02 rx [11061395.884710] R13: ffff9874ad283a60 R14: ffff9874ad283980 R15: ffff9874ad283d30 Jul 26 15:05:02 rx [11061395.892095] FS: 00007f1ef4a2e700(0000) GS:ffff987605e00000(0000) knlGS:0000000000000000 Jul 26 15:05:02 rx [11061395.900438] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Jul 26 15:05:02 rx [11061395.906435] CR2: 0000000000000020 CR3: 0000003e450ba003 CR4: 0000000000760ef0 Jul 26 15:05:02 rx [11061395.913822] PKRU: 55555554 Jul 26 15:05:02 rx [11061395.916786] Call Trace: Jul 26 15:05:02 rx [11061395.919488] Jul 26 15:05:02 rx [11061395.921765] ? show_regs.cold+0x1a/0x1f Jul 26 15:05:02 rx [11061395.925859] ? __die+0x90/0xd9 Jul 26 15:05:02 rx [11061395.929169] ? no_context+0x196/0x380 Jul 26 15:05:02 rx [11061395.933088] ? ip6_protocol_deliver_rcu+0x4e0/0x4e0 Jul 26 15:05:02 rx [11061395.938216] ? ip6_sublist_rcv_finish+0x3d/0x50 Jul 26 15:05:02 rx [11061395.943000] ? __bad_area_nosemaphore+0x50/0x1a0 Jul 26 15:05:02 rx [11061395.947873] ? bad_area_nosemaphore+0x16/0x20 Jul 26 15:05:02 rx [11061395.952486] ? do_user_addr_fault+0x267/0x450 Jul 26 15:05:02 rx [11061395.957104] ? ipv6_list_rcv+0x112/0x140 Jul 26 15:05:02 rx [11061395.961279] ? __do_page_fault+0x58/0x90 Jul 26 15:05:02 rx [11061395.965458] ? do_page_fault+0x2c/0xe0 Jul 26 15:05:02 rx [11061395.969465] ? page_fault+0x34/0x40 Jul 26 15:05:02 rx [11061395.973217] ? tcp_rearm_rto+0xe4/0x160 Jul 26 15:05:02 rx [11061395.977313] ? tcp_rearm_rto+0xe4/0x160 Jul 26 15:05:02 rx [11061395.981408] tcp_send_loss_probe+0x10b/0x220 Jul 26 15:05:02 rx [11061395.985937] tcp_write_timer_handler+0x1b4/0x240 Jul 26 15:05:02 rx [11061395.990809] tcp_write_timer+0x9e/0xe0 Jul 26 15:05:02 rx [11061395.994814] ? tcp_write_timer_handler+0x240/0x240 Jul 26 15:05:02 rx [11061395.999866] call_timer_fn+0x32/0x130 Jul 26 15:05:02 rx [11061396.003782] __run_timers.part.0+0x180/0x280 Jul 26 15:05:02 rx [11061396.008309] ? recalibrate_cpu_khz+0x10/0x10 Jul 26 15:05:02 rx [11061396.012841] ? native_x2apic_icr_write+0x30/0x30 Jul 26 15:05:02 rx [11061396.017718] ? lapic_next_event+0x21/0x30 Jul 26 15:05:02 rx [11061396.021984] ? clockevents_program_event+0x8f/0xe0 Jul 26 15:05:02 rx [11061396.027035] run_timer_softirq+0x2a/0x50 Jul 26 15:05:02 rx [11061396.031212] __do_softirq+0xd1/0x2c1 Jul 26 15:05:02 rx [11061396.035044] do_softirq_own_stack+0x2a/0x40 Jul 26 15:05:02 rx [11061396.039480] Jul 26 15:05:02 rx [11061396.041840] do_softirq.part.0+0x46/0x50 Jul 26 15:05:02 rx [11061396.046022] __local_bh_enable_ip+0x50/0x60 Jul 26 15:05:02 rx [11061396.050460] _raw_spin_unlock_bh+0x1e/0x20 Jul 26 15:05:02 rx [11061396.054817] nf_conntrack_tcp_packet+0x29e/0xbe0 [nf_conntrack] Jul 26 15:05:02 rx [11061396.060994] ? get_l4proto+0xe7/0x190 [nf_conntrack] Jul 26 15:05:02 rx [11061396.066220] nf_conntrack_in+0xe9/0x670 [nf_conntrack] Jul 26 15:05:02 rx [11061396.071618] ipv6_conntrack_local+0x14/0x20 [nf_conntrack] Jul 26 15:05:02 rx [11061396.077356] nf_hook_slow+0x45/0xb0 Jul 26 15:05:02 rx [11061396.081098] ip6_xmit+0x3f0/0x5d0 Jul 26 15:05:02 rx [11061396.084670] ? ipv6_anycast_cleanup+0x50/0x50 Jul 26 15:05:02 rx [11061396.089282] ? __sk_dst_check+0x38/0x70 Jul 26 15:05:02 rx [11061396.093381] ? inet6_csk_route_socket+0x13b/0x200 Jul 26 15:05:02 rx [11061396.098346] inet6_csk_xmit+0xa7/0xf0 Jul 26 15:05:02 rx [11061396.102263] __tcp_transmit_skb+0x550/0xb30 Jul 26 15:05:02 rx [11061396.106701] tcp_write_xmit+0x3c6/0xc20 Jul 26 15:05:02 rx [11061396.110792] ? __alloc_skb+0x98/0x1d0 Jul 26 15:05:02 rx [11061396.114708] __tcp_push_pending_frames+0x37/0x100 Jul 26 15:05:02 rx [11061396.119667] tcp_push+0xfd/0x100 Jul 26 15:05:02 rx [11061396.123150] tcp_sendmsg_locked+0xc70/0xdd0 Jul 26 15:05:02 rx [11061396.127588] tcp_sendmsg+0x2d/0x50 Jul 26 15:05:02 rx [11061396.131245] inet6_sendmsg+0x43/0x70 Jul 26 15:05:02 rx [11061396.135075] __sock_sendmsg+0x48/0x70 Jul 26 15:05:02 rx [11061396.138994] ____sys_sendmsg+0x212/0x280 Jul 26 15:05:02 rx [11061396.143172] ___sys_sendmsg+0x88/0xd0 Jul 26 15:05:02 rx [11061396.147098] ? __seccomp_filter+0x7e/0x6b0 Jul 26 15:05:02 rx [11061396.151446] ? __switch_to+0x39c/0x460 Jul 26 15:05:02 rx [11061396.155453] ? __switch_to_asm+0x42/0x80 Jul 26 15:05:02 rx [11061396.159636] ? __switch_to_asm+0x5a/0x80 Jul 26 15:05:02 rx [11061396.163816] __sys_sendmsg+0x5c/0xa0 Jul 26 15:05:02 rx [11061396.167647] __x64_sys_sendmsg+0x1f/0x30 Jul 26 15:05:02 rx [11061396.171832] do_syscall_64+0x57/0x190 Jul 26 15:05:02 rx [11061396.175748] entry_SYSCALL_64_after_hwframe+0x5c/0xc1 Jul 26 15:05:02 rx [11061396.181055] RIP: 0033:0x7f1ef692618d Jul 26 15:05:02 rx [11061396.184893] Code: 28 89 54 24 1c 48 89 74 24 10 89 7c 24 08 e8 ca ee ff ff 8b 54 24 1c 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 2f 44 89 c7 48 89 44 24 08 e8 fe ee ff ff 48 Jul 26 15:05:02 rx [11061396.203889] RSP: 002b:00007f1ef4a26aa0 EFLAGS: 00000293 ORIG_RAX: 000000000000002e Jul 26 15:05:02 rx [11061396.211708] RAX: ffffffffffffffda RBX: 000000000000084b RCX: 00007f1ef692618d Jul 26 15:05:02 rx [11061396.219091] RDX: 0000000000004000 RSI: 00007f1ef4a26b10 RDI: 0000000000000275 Jul 26 15:05:02 rx [11061396.226475] RBP: 0000000000004000 R08: 0000000000000000 R09: 0000000000000020 Jul 26 15:05:02 rx [11061396.233859] R10: 0000000000000000 R11: 0000000000000293 R12: 000000000000084b Jul 26 15:05:02 rx [11061396.241243] R13: 00007f1ef4a26b10 R14: 0000000000000275 R15: 000055592030f1e8 Jul 26 15:05:02 rx [11061396.248628] Modules linked in: vrf bridge stp llc vxlan ip6_udp_tunnel udp_tunnel nls_iso8859_1 amd64_edac_mod edac_mce_amd kvm_amd kvm crct10dif_pclmul ghash_clmulni_intel aesni_intel crypto_simd cryptd glue_helper wmi_bmof ipmi_ssif input_leds joydev rndis_host cdc_ether usbnet mii ast drm_vram_helper ttm drm_kms_helper i2c_algo_bit fb_sys_fops syscopyarea sysfillrect sysimgblt ccp mac_hid ipmi_si ipmi_devintf ipmi_msghandler nft_ct sch_fq_codel nf_tables_set nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink ramoops reed_solomon efi_pstore drm ip_tables x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid0 multipath linear mlx5_ib ib_uverbs ib_core raid1 mlx5_core hid_generic pci_hyperv_intf crc32_pclmul tls usbhid ahci mlxfw bnxt_en libahci hid nvme i2c_piix4 nvme_core wmi Jul 26 15:05:02 rx [11061396.324334] CR2: 0000000000000020 Jul 26 15:05:02 rx [11061396.327944] ---[ end trace 68a2b679d1cfb4f1 ]--- Jul 26 15:05:02 rx [11061396.433435] RIP: 0010:tcp_rearm_rto+0xe4/0x160 Jul 26 15:05:02 rx [11061396.438137] Code: 87 ca 04 00 00 00 5b 41 5c 41 5d 5d c3 c3 49 8b bc 24 40 06 00 00 eb 8d 48 bb cf f7 53 e3 a5 9b c4 20 4c 89 ef e8 0c fe 0e 00 <48> 8b 78 20 48 c1 ef 03 48 89 f8 41 8b bc 24 80 04 00 00 48 f7 e3 Jul 26 15:05:02 rx [11061396.457144] RSP: 0018:ffffb75d40003e08 EFLAGS: 00010246 Jul 26 15:05:02 rx [11061396.462629] RAX: 0000000000000000 RBX: 20c49ba5e353f7cf RCX: 0000000000000000 Jul 26 15:05:02 rx [11061396.470012] RDX: 0000000062177c30 RSI: 000000000000231c RDI: ffff9874ad283a60 Jul 26 15:05:02 rx [11061396.477396] RBP: ffffb75d40003e20 R08: 0000000000000000 R09: ffff987605e20aa8 Jul 26 15:05:02 rx [11061396.484779] R10: ffffb75d40003f00 R11: ffffb75d4460f740 R12: ffff9874ad283900 Jul 26 15:05:02 rx [11061396.492164] R13: ffff9874ad283a60 R14: ffff9874ad283980 R15: ffff9874ad283d30 Jul 26 15:05:02 rx [11061396.499547] FS: 00007f1ef4a2e700(0000) GS:ffff987605e00000(0000) knlGS:0000000000000000 Jul 26 15:05:02 rx [11061396.507886] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Jul 26 15:05:02 rx [11061396.513884] CR2: 0000000000000020 CR3: 0000003e450ba003 CR4: 0000000000760ef0 Jul 26 15:05:02 rx [11061396.521267] PKRU: 55555554 Jul 26 15:05:02 rx [11061396.524230] Kernel panic - not syncing: Fatal exception in interrupt Jul 26 15:05:02 rx [11061396.530885] Kernel Offset: 0x1b200000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) Jul 26 15:05:03 rx [11061396.660181] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]--- After we hit this we disabled TLP by setting tcp_early_retrans to 0 and then hit the crash in the RACK case: Aug 7 07:26:16 rx [1006006.265582] BUG: kernel NULL pointer dereference, address: 0000000000000020 Aug 7 07:26:16 rx [1006006.272719] #PF: supervisor read access in kernel mode Aug 7 07:26:16 rx [1006006.278030] #PF: error_code(0x0000) - not-present page Aug 7 07:26:16 rx [1006006.283343] PGD 0 P4D 0 Aug 7 07:26:16 rx [1006006.286057] Oops: 0000 [#1] SMP NOPTI Aug 7 07:26:16 rx [1006006.289896] CPU: 5 PID: 0 Comm: swapper/5 Tainted: G W 5.4.0-174-generic #193-Ubuntu Aug 7 07:26:16 rx [1006006.299107] Hardware name: Supermicro SMC 2x26 os-gen8 64C NVME-Y 256G/H12SSW-NTR, BIOS 2.5.V1.2U.NVMe.UEFI 05/09/2023 Aug 7 07:26:16 rx [1006006.309970] RIP: 0010:tcp_rearm_rto+0xe4/0x160 Aug 7 07:26:16 rx [1006006.314584] Code: 87 ca 04 00 00 00 5b 41 5c 41 5d 5d c3 c3 49 8b bc 24 40 06 00 00 eb 8d 48 bb cf f7 53 e3 a5 9b c4 20 4c 89 ef e8 0c fe 0e 00 <48> 8b 78 20 48 c1 ef 03 48 89 f8 41 8b bc 24 80 04 00 00 48 f7 e3 Aug 7 07:26:16 rx [1006006.333499] RSP: 0018:ffffb42600a50960 EFLAGS: 00010246 Aug 7 07:26:16 rx [1006006.338895] RAX: 0000000000000000 RBX: 20c49ba5e353f7cf RCX: 0000000000000000 Aug 7 07:26:16 rx [1006006.346193] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff92d687ed8160 Aug 7 07:26:16 rx [1006006.353489] RBP: ffffb42600a50978 R08: 0000000000000000 R09: 00000000cd896dcc Aug 7 07:26:16 rx [1006006.360786] R10: ffff92dc3404f400 R11: 0000000000000001 R12: ffff92d687ed8000 Aug 7 07:26:16 rx [1006006.368084] R13: ffff92d687ed8160 R14: 00000000cd896dcc R15: 00000000cd8fca81 Aug 7 07:26:16 rx [1006006.375381] FS: 0000000000000000(0000) GS:ffff93158ad40000(0000) knlGS:0000000000000000 Aug 7 07:26:16 rx [1006006.383632] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Aug 7 07:26:16 rx [1006006.389544] CR2: 0000000000000020 CR3: 0000003e775ce006 CR4: 0000000000760ee0 Aug 7 07:26:16 rx [1006006.396839] PKRU: 55555554 Aug 7 07:26:16 rx [1006006.399717] Call Trace: Aug 7 07:26:16 rx [1006006.402335] Aug 7 07:26:16 rx [1006006.404525] ? show_regs.cold+0x1a/0x1f Aug 7 07:26:16 rx [1006006.408532] ? __die+0x90/0xd9 Aug 7 07:26:16 rx [1006006.411760] ? no_context+0x196/0x380 Aug 7 07:26:16 rx [1006006.415599] ? __bad_area_nosemaphore+0x50/0x1a0 Aug 7 07:26:16 rx [1006006.420392] ? _raw_spin_lock+0x1e/0x30 Aug 7 07:26:16 rx [1006006.424401] ? bad_area_nosemaphore+0x16/0x20 Aug 7 07:26:16 rx [1006006.428927] ? do_user_addr_fault+0x267/0x450 Aug 7 07:26:16 rx [1006006.433450] ? __do_page_fault+0x58/0x90 Aug 7 07:26:16 rx [1006006.437542] ? do_page_fault+0x2c/0xe0 Aug 7 07:26:16 rx [1006006.441470] ? page_fault+0x34/0x40 Aug 7 07:26:16 rx [1006006.445134] ? tcp_rearm_rto+0xe4/0x160 Aug 7 07:26:16 rx [1006006.449145] tcp_ack+0xa32/0xb30 Aug 7 07:26:16 rx [1006006.452542] tcp_rcv_established+0x13c/0x670 Aug 7 07:26:16 rx [1006006.456981] ? sk_filter_trim_cap+0x48/0x220 Aug 7 07:26:16 rx [1006006.461419] tcp_v6_do_rcv+0xdb/0x450 Aug 7 07:26:16 rx [1006006.465257] tcp_v6_rcv+0xc2b/0xd10 Aug 7 07:26:16 rx [1006006.468918] ip6_protocol_deliver_rcu+0xd3/0x4e0 Aug 7 07:26:16 rx [1006006.473706] ip6_input_finish+0x15/0x20 Aug 7 07:26:16 rx [1006006.477710] ip6_input+0xa2/0xb0 Aug 7 07:26:16 rx [1006006.481109] ? ip6_protocol_deliver_rcu+0x4e0/0x4e0 Aug 7 07:26:16 rx [1006006.486151] ip6_sublist_rcv_finish+0x3d/0x50 Aug 7 07:26:16 rx [1006006.490679] ip6_sublist_rcv+0x1aa/0x250 Aug 7 07:26:16 rx [1006006.494779] ? ip6_rcv_finish_core.isra.0+0xa0/0xa0 Aug 7 07:26:16 rx [1006006.499828] ipv6_list_rcv+0x112/0x140 Aug 7 07:26:16 rx [1006006.503748] __netif_receive_skb_list_core+0x1a4/0x250 Aug 7 07:26:16 rx [1006006.509057] netif_receive_skb_list_internal+0x1a1/0x2b0 Aug 7 07:26:16 rx [1006006.514538] gro_normal_list.part.0+0x1e/0x40 Aug 7 07:26:16 rx [1006006.519068] napi_complete_done+0x91/0x130 Aug 7 07:26:16 rx [1006006.523352] mlx5e_napi_poll+0x18e/0x610 [mlx5_core] Aug 7 07:26:16 rx [1006006.528481] net_rx_action+0x142/0x390 Aug 7 07:26:16 rx [1006006.532398] __do_softirq+0xd1/0x2c1 Aug 7 07:26:16 rx [1006006.536142] irq_exit+0xae/0xb0 Aug 7 07:26:16 rx [1006006.539452] do_IRQ+0x5a/0xf0 Aug 7 07:26:16 rx [1006006.542590] common_interrupt+0xf/0xf Aug 7 07:26:16 rx [1006006.546421] Aug 7 07:26:16 rx [1006006.548695] RIP: 0010:native_safe_halt+0xe/0x10 Aug 7 07:26:16 rx [1006006.553399] Code: 7b ff ff ff eb bd 90 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 36 2c 50 00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d 26 2c 50 00 fb f4 90 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 53 e8 dd 5e 61 ff 65 Aug 7 07:26:16 rx [1006006.572309] RSP: 0018:ffffb42600177e70 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffc2 Aug 7 07:26:16 rx [1006006.580040] RAX: ffffffff8ed08b20 RBX: 0000000000000005 RCX: 0000000000000001 Aug 7 07:26:16 rx [1006006.587337] RDX: 00000000f48eeca2 RSI: 0000000000000082 RDI: 0000000000000082 Aug 7 07:26:16 rx [1006006.594635] RBP: ffffb42600177e90 R08: 0000000000000000 R09: 000000000000020f Aug 7 07:26:16 rx [1006006.601931] R10: 0000000000100000 R11: 0000000000000000 R12: 0000000000000005 Aug 7 07:26:16 rx [1006006.609229] R13: ffff93157deb5f00 R14: 0000000000000000 R15: 0000000000000000 Aug 7 07:26:16 rx [1006006.616530] ? __cpuidle_text_start+0x8/0x8 Aug 7 07:26:16 rx [1006006.620886] ? default_idle+0x20/0x140 Aug 7 07:26:16 rx [1006006.624804] arch_cpu_idle+0x15/0x20 Aug 7 07:26:16 rx [1006006.628545] default_idle_call+0x23/0x30 Aug 7 07:26:16 rx [1006006.632640] do_idle+0x1fb/0x270 Aug 7 07:26:16 rx [1006006.636035] cpu_startup_entry+0x20/0x30 Aug 7 07:26:16 rx [1006006.640126] start_secondary+0x178/0x1d0 Aug 7 07:26:16 rx [1006006.644218] secondary_startup_64+0xa4/0xb0 Aug 7 07:26:17 rx [1006006.648568] Modules linked in: vrf bridge stp llc vxlan ip6_udp_tunnel udp_tunnel nls_iso8859_1 nft_ct amd64_edac_mod edac_mce_amd kvm_amd kvm crct10dif_pclmul ghash_clmulni_intel aesni_intel crypto_simd cryptd glue_helper wmi_bmof ipmi_ssif input_leds joydev rndis_host cdc_ether usbnet ast mii drm_vram_helper ttm drm_kms_helper i2c_algo_bit fb_sys_fops syscopyarea sysfillrect sysimgblt ccp mac_hid ipmi_si ipmi_devintf ipmi_msghandler sch_fq_codel nf_tables_set nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink ramoops reed_solomon efi_pstore drm ip_tables x_tables autofs4 raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid0 multipath linear mlx5_ib ib_uverbs ib_core raid1 hid_generic mlx5_core pci_hyperv_intf crc32_pclmul usbhid ahci tls mlxfw bnxt_en hid libahci nvme i2c_piix4 nvme_core wmi [last unloaded: cpuid] Aug 7 07:26:17 rx [1006006.726180] CR2: 0000000000000020 Aug 7 07:26:17 rx [1006006.729718] ---[ end trace e0e2e37e4e612984 ]--- Prior to seeing the first crash and on other machines we also see the warning in tcp_send_loss_probe() where packets_out is non-zero, but both transmit and retrans queues are empty so we know the box is seeing some accounting issue in this area: Jul 26 09:15:27 kernel: ------------[ cut here ]------------ Jul 26 09:15:27 kernel: invalid inflight: 2 state 1 cwnd 68 mss 8988 Jul 26 09:15:27 kernel: WARNING: CPU: 16 PID: 0 at net/ipv4/tcp_output.c:2605 tcp_send_loss_probe+0x214/0x220 Jul 26 09:15:27 kernel: Modules linked in: vrf bridge stp llc vxlan ip6_udp_tunnel udp_tunnel nls_iso8859_1 nft_ct amd64_edac_mod edac_mce_amd kvm_amd kvm crct10dif_pclmul ghash_clmulni_intel aesni_intel crypto_simd cryptd glue_helper wmi_bmof ipmi_ssif joydev input_leds rndis_host cdc_ether usbnet mii ast drm_vram_helper ttm drm_kms_he> Jul 26 09:15:27 kernel: CPU: 16 PID: 0 Comm: swapper/16 Not tainted 5.4.0-174-generic #193-Ubuntu Jul 26 09:15:27 kernel: Hardware name: Supermicro SMC 2x26 os-gen8 64C NVME-Y 256G/H12SSW-NTR, BIOS 2.5.V1.2U.NVMe.UEFI 05/09/2023 Jul 26 09:15:27 kernel: RIP: 0010:tcp_send_loss_probe+0x214/0x220 Jul 26 09:15:27 kernel: Code: 08 26 01 00 75 e2 41 0f b6 54 24 12 41 8b 8c 24 c0 06 00 00 45 89 f0 48 c7 c7 e0 b4 20 a7 c6 05 8d 08 26 01 01 e8 4a c0 0f 00 <0f> 0b eb ba 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 Jul 26 09:15:27 kernel: RSP: 0018:ffffb7838088ce00 EFLAGS: 00010286 Jul 26 09:15:27 kernel: RAX: 0000000000000000 RBX: ffff9b84b5630430 RCX: 0000000000000006 Jul 26 09:15:27 kernel: RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff9b8e4621c8c0 Jul 26 09:15:27 kernel: RBP: ffffb7838088ce18 R08: 0000000000000927 R09: 0000000000000004 Jul 26 09:15:27 kernel: R10: 0000000000000000 R11: 0000000000000001 R12: ffff9b84b5630000 Jul 26 09:15:27 kernel: R13: 0000000000000000 R14: 000000000000231c R15: ffff9b84b5630430 Jul 26 09:15:27 kernel: FS: 0000000000000000(0000) GS:ffff9b8e46200000(0000) knlGS:0000000000000000 Jul 26 09:15:27 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Jul 26 09:15:27 kernel: CR2: 000056238cec2380 CR3: 0000003e49ede005 CR4: 0000000000760ee0 Jul 26 09:15:27 kernel: PKRU: 55555554 Jul 26 09:15:27 kernel: Call Trace: Jul 26 09:15:27 kernel: <IRQ> Jul 26 09:15:27 kernel: ? show_regs.cold+0x1a/0x1f Jul 26 09:15:27 kernel: ? __warn+0x98/0xe0 Jul 26 09:15:27 kernel: ? tcp_send_loss_probe+0x214/0x220 Jul 26 09:15:27 kernel: ? report_bug+0xd1/0x100 Jul 26 09:15:27 kernel: ? do_error_trap+0x9b/0xc0 Jul 26 09:15:27 kernel: ? do_invalid_op+0x3c/0x50 Jul 26 09:15:27 kernel: ? tcp_send_loss_probe+0x214/0x220 Jul 26 09:15:27 kernel: ? invalid_op+0x1e/0x30 Jul 26 09:15:27 kernel: ? tcp_send_loss_probe+0x214/0x220 Jul 26 09:15:27 kernel: tcp_write_timer_handler+0x1b4/0x240 Jul 26 09:15:27 kernel: tcp_write_timer+0x9e/0xe0 Jul 26 09:15:27 kernel: ? tcp_write_timer_handler+0x240/0x240 Jul 26 09:15:27 kernel: call_timer_fn+0x32/0x130 Jul 26 09:15:27 kernel: __run_timers.part.0+0x180/0x280 Jul 26 09:15:27 kernel: ? timerqueue_add+0x9b/0xb0 Jul 26 09:15:27 kernel: ? enqueue_hrtimer+0x3d/0x90 Jul 26 09:15:27 kernel: ? do_error_trap+0x9b/0xc0 Jul 26 09:15:27 kernel: ? do_invalid_op+0x3c/0x50 Jul 26 09:15:27 kernel: ? tcp_send_loss_probe+0x214/0x220 Jul 26 09:15:27 kernel: ? invalid_op+0x1e/0x30 Jul 26 09:15:27 kernel: ? tcp_send_loss_probe+0x214/0x220 Jul 26 09:15:27 kernel: tcp_write_timer_handler+0x1b4/0x240 Jul 26 09:15:27 kernel: tcp_write_timer+0x9e/0xe0 Jul 26 09:15:27 kernel: ? tcp_write_timer_handler+0x240/0x240 Jul 26 09:15:27 kernel: call_timer_fn+0x32/0x130 Jul 26 09:15:27 kernel: __run_timers.part.0+0x180/0x280 Jul 26 09:15:27 kernel: ? timerqueue_add+0x9b/0xb0 Jul 26 09:15:27 kernel: ? enqueue_hrtimer+0x3d/0x90 Jul 26 09:15:27 kernel: ? recalibrate_cpu_khz+0x10/0x10 Jul 26 09:15:27 kernel: ? ktime_get+0x3e/0xa0 Jul 26 09:15:27 kernel: ? native_x2apic_icr_write+0x30/0x30 Jul 26 09:15:27 kernel: run_timer_softirq+0x2a/0x50 Jul 26 09:15:27 kernel: __do_softirq+0xd1/0x2c1 Jul 26 09:15:27 kernel: irq_exit+0xae/0xb0 Jul 26 09:15:27 kernel: smp_apic_timer_interrupt+0x7b/0x140 Jul 26 09:15:27 kernel: apic_timer_interrupt+0xf/0x20 Jul 26 09:15:27 kernel: </IRQ> Jul 26 09:15:27 kernel: RIP: 0010:native_safe_halt+0xe/0x10 Jul 26 09:15:27 kernel: Code: 7b ff ff ff eb bd 90 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 36 2c 50 00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d 26 2c 50 00 fb f4 <c3> 90 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 53 e8 dd 5e 61 ff 65 Jul 26 09:15:27 kernel: RSP: 0018:ffffb783801cfe70 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 Jul 26 09:15:27 kernel: RAX: ffffffffa6908b20 RBX: 0000000000000010 RCX: 0000000000000001 Jul 26 09:15:27 kernel: RDX: 000000006fc0c97e RSI: 0000000000000082 RDI: 0000000000000082 Jul 26 09:15:27 kernel: RBP: ffffb783801cfe90 R08: 0000000000000000 R09: 0000000000000225 Jul 26 09:15:27 kernel: R10: 0000000000100000 R11: 0000000000000000 R12: 0000000000000010 Jul 26 09:15:27 kernel: R13: ffff9b8e390b0000 R14: 0000000000000000 R15: 0000000000000000 Jul 26 09:15:27 kernel: ? __cpuidle_text_start+0x8/0x8 Jul 26 09:15:27 kernel: ? default_idle+0x20/0x140 Jul 26 09:15:27 kernel: arch_cpu_idle+0x15/0x20 Jul 26 09:15:27 kernel: default_idle_call+0x23/0x30 Jul 26 09:15:27 kernel: do_idle+0x1fb/0x270 Jul 26 09:15:27 kernel: cpu_startup_entry+0x20/0x30 Jul 26 09:15:27 kernel: start_secondary+0x178/0x1d0 Jul 26 09:15:27 kernel: secondary_startup_64+0xa4/0xb0 Jul 26 09:15:27 kernel: ---[ end trace e7ac822987e33be1 ]--- The NULL ptr deref is coming from tcp_rto_delta_us() attempting to pull an skb off the head of the retransmit queue and then dereferencing that skb to get the skb_mstamp_ns value via tcp_skb_timestamp_us(skb). The crash is the same one that was reported a # of years ago here: https://lore.kernel.org/netdev/86c0f836-9a7c-438b-d81a-839be45f1f58@gmail.com/T/#t and the kernel we're running has the fix which was added to resolve this issue. Unfortunately we've been unsuccessful so far in reproducing this problem in the lab and do not have the luxury of pushing out a new kernel to try and test if newer kernels resolve this issue at the moment. I realize this is a report against both an Ubuntu kernel and also an older 5.4 kernel. I have reported this issue to Ubuntu here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2077657 however I feel like since this issue has possibly cropped up again it makes sense to build in some protection in this path (even on the latest kernel versions) since the code in question just blindly assumes there's a valid skb without testing if it's NULL b/f it looks at the timestamp. Given we have seen crashes in this path before and now this case it seems like we should protect ourselves for when packets_out accounting is incorrect. While we should fix that root cause we should also just make sure the skb is not NULL before dereferencing it. Also add a warn once here to capture some information if/when the problem case is hit again. Fixes: e1a10ef7fa87 ("tcp: introduce tcp_rto_delta_us() helper for xmit timer fix") Signed-off-by: Josh Hunt <johunt@akamai.com> --- v3: Added fixes tag and more packet accounting info as requested by Neal Cardwell. Also updated rto calcs to reflect original code. v2: Removed cover letter and added context from original cover letter to commit msg. include/net/tcp.h | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)